suddenly rough idle

I have a 96 blazer with 4.3 engine. The engine is new, but due to leaking oil lines, and me forgetting to check oil, I ran it 3 qt low. Now the lifters are constantly rattling. That is backround info.

Yesterday all of a sudden the idle went really rough. Just after I started it up. There is a loss of power when pulling out from an intersection. But it seems ok at curze. I though maybe EGR, I replaced the gasket and cleaned the egr with carb cleaner.

The spark plugs, wires and dist cap are only 1 yr old with about 15k miles on it. The engine was replace witha Jasper about 17k miles ago.

Is it vaccuum, egr or what?

I am sorry to ask a question which surely has been asked before, but I am confused with the Google search engine on this website.

*also the check engine light now flashes at me, before this it stayed on. The autozone guy said it was, "random miss fire" & "too lean" there might have been a third error.

is it missfiring at all.

It is real rough idle, but it appears to cruise just fine. I am not sure how else to describe it or to find out if it is actually misfiring. Something suddenly changed on it yesterday. I turned the engine off and 20 minutes later when I started it up there was the rough idle. It actually makes the truck shake at an idle.

Could be EGR.You said you cleaned it.Was it bad(build up)if it was try cleaning the ports that go into the intak